If you don’t know what is the best wood to use for a job tell your timber merchant what you propose making and be guided by him.
You can buy timber already planed — called prepared or PAR (planed all round) — which saves a lot of working time because it has only to be glasspapered after assembly and before staining or painting. But this pre-planing slightly decreases the width and thickness. Tongued-and-grooved (T and G) and also shiplap suffer an even greater reduction because the size of the tongue is included in the overall quoted width of the board; and this will be lost when the tongue of one board is fitted into the groove of its neighbour.
For the best work specify quarter-sawn timber, the grain of which is narrower and closer than that of flat-sawn and does not show such wide, wandering whorls. It does not warp so readily and is easier to paint. The closer the grain lines, the better will the coating adhere and the smoother will be the finish. Flat-sawn timber is cheaper because it will produce more planks to a log, but the edges have a tendency to curl up on the bark side. No doubt you have noticed this with old floorboards.
Avoid sapwood, which is cut from the outer part of the trunk near the bark and shows streaks of another colour, generally light blue, which can discolour a subsequent coat of paint. Sapwood is not so strong as heartwood, which comes from the centre of the trunk. It is particularly unsuitable for floorboards and joists where there may be poor circulation and conditions favouring dry rot.
Timbers are classified as either hardwood or softwood — which is rather misleading because the former is not necessarily hard, though it usually is, and the latter not necessarily soft. Some softwoods are harder than some hardwoods. Yew has almost the toughness of oak, yet it is a softwood. On the other hand, balsa is so spongy that you can dent it with your fingernail, yet it is a hardwood. Hardwoods are so called because they come from deciduous broad-leaf trees and softwoods because they come from coniferous needle-leaf trees.
Of the two thousand species of timber grown throughout the world, here are a few of the greatest use for home improvement projects.
Ash. The light grey timber from the British tree is the best ash in the world. Being tough and elastic, it can be steamed into various shapes. When an ash tree has been pollarded, long straight boughs shoot up, which are used in the manufacture of ladders and handles of implements. As such work is done mostly by furniture and tool manufacturers who buy in bulk, you may have to shop round to get this timber. One disadvantage of it is surface splitting — as you will no doubt have noticed with the handle of a garden fork or spade.
Beech and birch. Reddish brown in colour. As these timbers are close-grained and easily bent they are employed largely in chair-making, but not for other furniture because of their liability to twist. They take stain and paint well. Birch is also used in cheap plywood, which is not so easy to paint.
Chestnut. White and rather woolly in texture but when used for cabinet-making it will take a good polish, and it carves well. In the old days milk pails were made of chestnut on account of its whiteness.
Elm. Pale brown in colour. Being tough and durable in wet conditions, it is used for weatherboarding and sheds. It does not split easily, though it has a tendency to warp. It used to be used for cartwheels and at one time elm pipes supplied London with water.
Harewood. See Sycamore (below).
Iroko. A strong timber for general joinery. Works easily.
Lime. Off-white in colour and, being soft and crisp under a cutting tool, it is admirable for carving. The inner bark (bast) is often woven into mats and used for tying up garden plants.
Mahogany. Popular for high-class furniture owing to its attractive colouring, varying from light to dark reddish brown.
British Honduras mahogany is generally considered the best for furniture and joinery, though it is scarce and expensive and is not used much as a veneer. One of the most stable of woods, easily worked, and also takes polish well. African mahoganies, which are more plentiful, include utile and sapele, but the latter is not so easy to work because its interlocking fibres tend to fur up when planed.
Oak. Very hard and strong and, when quarter-sawn, so-called red oak has a distinctive grain which makes it ideal for reproducing Tudor furniture. The colour of red oak is not red to start with but yellow and, after deepening to red, it eventually weathers to an attractive silver. Unfortunately it has a tendency to develop shakes (splits) unless well seasoned. White oak is close set and does not have the distinctive grain of red oak. British oak is about the strongest, but it is scarce and expensive owing to its slow rate of growth. European oaks (other than British) are more plentiful. American and Japanese are lighter in weight and easier to work. Sharp tools are needed for all oaks.
Ramin. Used as a cheap and good substitute for mahogany, teak and walnut.
Rosewood. A strong, red-brown timber with a distinctive grain which makes it admirable for cabinet-making. Not too easy to work with.
Sapele. See Mahogany (above).
Sycamore. Creamy in colour deepening in time to a deep yellow, sycamore has a silky surface and close grain. Of moderate strength, it is easy to work. Used for furniture-making. The highly decorative knotty parts of this timber can be fashioned into bowls and fancy box lids. When stained grey with salts of iron applied liberally, sycamore is called hare-wood. Salts of iron can be made by dissolving iron sulphate in water, or by steeping bits of iron in vinegar for a few days. Another way is to leave rusty nails in a jar of water for a week. You can also achieve an ebonized effect by treating the timber with a solution of tannic acid. When dry, rub down and polish or varnish. For making tannic acid, boil oak galls, oak bark or scraps of oak in water. In all cases the dark tone improves with time.
These treatments apply to other woods in addition to sycamore.
Teak. One of the most fashionable furniture timbers of today and, being strong and weather-resistant, it is used largely for garden furniture. When new it is a brownish yellow, with dark streaks giving it a greyish appearance, and the whole surface darkens with age. It is naturally oily and therefore not easy to glue. It requires a special teak sealer before painting — though, in the writer’s opinion, it is sacrilege to paint such a beautiful wood. For outside work it is far better to protect it with a madison sealeror teak oil.The latter preserves the original colour.
Utile. See Mahogany (above).
Walnut. Varies from brown to near-black and, having a distinctive grain structure, it is largely used for veneering. The most popular walnut is American ‘black’.
Larch. Being the heaviest and one of the most durable of softwoods, larch is often used for fences and boatbuilding. Red-brown in colour.
Parana. Though tough, parana is easy to work and virtually free from knots. As it does not stand up too well to weather and tends to warp, its use should be confined to indoor work: panelling and built-in furniture. Off-white in colour.
Scots Pine. Known as ‘redwood’ or deal. Yellowish white in colour. Used largely for the structural work of a house: roof timbers, floorboards, joists, doors and window frames, and also for the concealed parts of furniture. Easy to work but full of knots.
Spruce (Our Christmas tree). Yellowish in colour, soft and very durable, it is used largely for kitchen furniture and cupboards. Because of its light weight and great length, it is also employed in shipbuilding and ladder-making.
Too many spike knots (those showing at the edge of a plank and that have been sawn through): they are liable to come out, leaving a groove which can seriously weaken the timber.
Western Red Cedar. An excellent reddish brown wood with straight grain and few if any knots. Does not readily rot even if left unprotected in the open. For this reason it is ideal for fences, cladding, garden sheds and roof shingles. Inside it can be used for panelling and built-in furniture because it stands the effects of central heating better than other timbers.
Treatment for Knots
From the above you will see that parana pine and western red cedar are virtually free from knots, whereas Scots pine is full of them. If the knots are sound and not too numerous you need not worry. Where the timber is to be stained they add character and can be made to form part of the decoration; where painted, two applications of patent knotting over each knot (and under the primer) will be sufficient to seal them in. If, however, they are extremely resinous, pass the flame of a blowlamp over them to warm them up. As the resin bubbles to the surface wipe it off with white spirit before applying patent knotting.
The way to apply knotting so that a bump does not show through a subsequent paint-film is to use a rag wrapped round the index finger, and then the edges will ‘feather’ off. Make the first application solely over the knot. When dry — which will take only a few minutes — give a second application, this time increasing the area; but don’t go too far out because paint does not adhere well over the shellac content.
Where adhesion difficulties are experienced, mix an equal amount of finishing coat with the primer. This sticks better than wood primer which, on its own, must have a surface into which it can soak.
The type of knot to be wary about is that showing diagonal cracks through its cross-section, indicating that it is dead and may fall out. It is better to cut these out in advance and fill the aperture with a plug of wood glued in.